In a semiconductor factory or a FPD manufacturing factory, along with the developments of highly integrated devices, there have been strong demands for controlling environmental conditions, such as a cleanliness factor or temperature and moisture degrees, in high levels. Moreover, because of recent severe cost competitions in semiconductors or FPDs, there have been demands for reducing the construction cost of a clean room, that is, initial costs, and running costs of the clean room itself.
A full-face down flowing system, as shown in FIG. 29, has been proposed as a system for achieving a clean room having a high cleanliness factor. In this system, the air inside a ceiling chamber 102 is allowed to flow into a fan filter unit 103 from an air intake 104 of the fan filter unit 103 placed on a ceiling of a clean chamber 101, and is pressurized by a blower 105 placed inside the fan filter unit 103, and after dust has been removed by a high efficiency filter 106, clean air is allowed to flow into the clean chamber 101 vertically downward at a flow rate of, for example, about 0.25 to 0.5 m/s. Next, the air is allowed to flow into an under floor chamber 108 through a grating floor 107 of the clean chamber 101, and is returned to a ceiling chamber 102 through a return flow passage 109; thus, a circulating flow with such a structure is formed. With this circulating flow, since the same air has dust removed therefrom by the high efficiency filter 106 many times, the inside of the clean chamber 101 is maintained with a high cleanliness factor, after a lapse of predetermined time from the start of the operation of the clean room.
Moreover, heat radiating members 110, such as various IC manufacturing devices or various kinds of inspection devices, are installed on a grating floor 107 inside the clean chamber 101. Since the heat radiating members 110 sometimes use a toxic gas or the like, the air inside the clean chamber 101 is sucked into an exhaust guide flow passage 111 together with the toxic gas that has been properly treated, and is discharged out of the clean room through the exhaust guide flow passage 111 inside the under floor chamber 108 for the sake of safety. In order to control the pressure inside the clean chamber 101 to a predetermined value, air having virtually the same flow rate as the exhaust flow rate outward from the clean room is transported to the inside of the ceiling chamber 102 through a supply-air guide flow passage 112, and is supplied to the inside of the ceiling chamber 102 as supply air from a supply-air inlet placed in the supply-air guide flow passage 112. An external adjusting device 113, which adjusts outer air into air suitable for the clean room is installed in the supply-air guide flow passage 112.
Here, in the clean chamber 101, heat radiating members 110, such as IC manufacturing devices or various kinds of inspective devices, are installed, and depending on the kinds of the heat radiating members 110, the surface temperatures of some of these heat radiating members 110 tend to become about 25 degrees to about 100 degrees to cause considerable heat generation (for example, drying furnaces and the like) and to form heat generating sources in the clean chamber 101. Conventionally, waste heat, generated by these heat radiating members 110 (thermal sources) is naturally diffused in the clean room, and the entire clean chamber 101 has been temperature-adjusted. Here, the clean rooms to be used for IC manufacturing rooms, various kinds of inspection rooms or the like, of course, need a high cleanliness factor with respect to dust, fine particulates, and the like, and these also need to be always maintained in a predetermined range, with respect to moisture and temperature.
The circulating flow of the clean chamber 101 is warmed by thermal loads of the heat radiating members 110 inside the clean chamber 101 or auxiliary devices, such as pumps (not shown), installed inside the under floor chamber 108; therefore, the temperature of the circulating flow that is directed into the under floor chamber 108 through the grating floor 107 of the clean chamber 101 becomes slightly higher than the ambient temperature of the clean chamber 101. In order to return this to a predetermined temperature, an air-conditioning device 104 is controlled so that the temperature inside the clean chamber 101 is kept constant.
As described above, in order to maintain the clean room environment, the clean room is provided with an air purifying device, such as the fan filter unit 103, having the high efficiency filter 106, and an air-conditioning device 114 that can control the temperature of air.
In such a conventional clean room, since a clean air flow is supplied to the clean chamber 101 at a uniform flow rate from the high efficiency filter 106 toward an under floor space 108, as shown in FIG. 30, the clean air flow is disturbed on the upper side of the heat radiating members 110, such as production facilities, as indicated by arrows “a” of solid lines in FIG. 30 by ascending air flows caused by heat generation or heat radiating from the heat radiating members 110 such as production facilities, with the result that pollutants, such as dust and chemical substances, generated on the upper portions of the heat radiating members 110 or the periphery thereof, tend to drop on the heat radiating members 110 as indicated by arrows “b” of dotted lines, resulting in adverse effects to the clean environment.
As a method for protecting the clean environment of the clean chamber 101 from pollutants, such as dust and chemical substances, a diffusion preventive method has been proposed (for example, see Patent Document 1) in which an air suction means (not shown) for sucking air containing pollutants such as dust and chemical substances on the upper portion of the heat radiating member 110 is disposed on the filter unit 103 on the upper side of the heat radiating member 110 so that the air containing pollutants such as dust and chemical substances on the upper side of the heat radiating member 110 is sucked from the filter unit 103 located on the upper side of the heat radiating member 110, and the pollutants such as dust and chemical substances are consequently captured by the high efficiency filter 106, and prevented from being diffused to the clean chamber 101.    Patent Document 1: JP-A No. 8-247512
However, in an attempt to suck air containing pollutants, such as dust and chemical substances, through the filter unit 103 on the upper side of the heat radiating member 110, although air located close to the filter unit 103 can be sucked sufficiently, air close to the upper portion of the heat radiating member 110 is located at a position far from the filter unit 103, with the result that the suction force becomes insufficient on the air close to the upper portion of the heat radiating member 110, failing to sufficiently suck the air located close to the upper portion of the heat radiating member 110.
As a result, air that contains pollutants, such as dust and chemical substances, on the upper portion of the heat radiating member 110, tends to drift on the upper side of the heat radiating member 110 for a long period of time, due to whirling air flows, thermal convections, or the like generated on the upper portion of the heat radiating member 110. Consequently, the concentration of dust, chemical substances, or the like in the air increases, with the result that gigantic size or weight increases due to collision among dust, chemical substances, or the like cause the dust or chemical substances or the like to freely fall down finally to adhere onto a wafer manufactured in the heat radiating member 110, failing to satisfy necessary quality required for the wafer or sufficient productivity thereof.
At present, the wiring pattern pitch on the wafer is about 50 nanometers, which corresponds to an ultra fine structure, and when pollutants such as dust or chemical substances having a size larger than the wiring pattern pitch fall on the wafer, the wafer tends to be short-circuited by the pollutants, such as dust or chemical substances, to cause an abnormal heat generation or burning.